The invention relates to medical devices, and more particularly to introducer sheaths and the like.
Introducer sheaths are used as conduits for the placement of intravascular medical devices into venous or arterial systems following percutaneous access using the Seldinger technique. The introducer sheath is placed into a major blood vessel and the introduced device is then advanced from the distal end of the sheath and maneuvered to the target site by the physician, usually under fluoroscopy. In the case of placement of devices such as pacemaker and defibrillator leads which have large proximal connectors, splittable sheaths are used so that the sheath can be removed from the patient without disturbing the lead which must be left in place.
While current introducer sheaths for placing pacemaker leads and other intravascular devices are adequate for most applications, new pacing technologies and strategies, such as Intracoronary Cardioverter Defibrillation (ICD) and biventricular pacing, have been developed that require placing leads into the coronary sinus or into the coronary vessels themselves. Accessing these anatomical sites is difficult to impossible with current introducer devices whose function is generally limited to establishing a conduit through a relatively large vessel to site that is relative easy to access. One problem is that pacemaker leads and other such devices are not particularly designed to have good pushability and torqueability. This especially true for leads inserted into or via the coronary sinus since they are generally thinner and even more flexible than their standard counterparts. While the reduced pushability and torqueability does not normally pose a concern regarding placement of right atrial and ventricular leads, it can be a problem when placing a lead to stimulate the left side of the heart. For example, one method is to access the peripheral or central vessel using a standard splittable sheath, as is currently done, then trying to push and maneuver the lead further, to enter the ostium of the coronary sinus. This approach has proven to be very time-consuming and quite difficult to accomplish, especially if the cardiac vessels are to be accessed. In the case of standard straight splittable sheaths made of polytetrafluoroethylene (PTFE) such as a PEEL-AWAY(trademark) Introducer Sheath (Cook Incorporated, Bloomington, Ind.), merely lengthening the sheath creates difficulties in that long PTFE sheaths are prone to kinking when being negotiated through a tortuous path, while the pre-scored sheaths made from other materials lack the pushability and torqueability to be guided through such a long, tortuous path. While adding a curve to the PTFE introducer will help in negotiating an initial tortuous bend, such as found in the subclavian and innominate veins, when a second, distal tortuous turn is required to access the target site, such as in the right atrium, the introducer sheath is not designed to make that bend. Additionally, to access a smaller target vessel such as the coronary sinus, a small introducer sheath is required that would lack the pushability and torqueability to be successfully maneuvered to that site without being prone to kinking. A second method has been to use a preformed guiding catheter to access the coronary sinus and associated vessels, then introducing the lead into the guiding catheter for placement. The primary disadvantage with this approach is that it is very difficult to remove the guiding catheter, which is not splittable, over the lead without dislodging it from the target site due to the amount of friction between the devices.
What is needed is an introducer system that can provide quicker and easier placement of a pacing lead or other device through a complex tortuous path to a remote anatomical location, especially where the target location requires a small-diameter introducer. Desirable properties of such a system would include splittability, resistance to kinking, minimal blood loss, and the ability to track over a wire guide to a precise location within a narrow vessel.
The foregoing problems are also solved and a technical advance is achieved in an introducer apparatus that includes co-extending splittable introducer sheaths, each having a different configurations. The use of co-extending introducers, whether coaxially arranged or coupled in another manner, permits advantageous use of the different properties or configurations of each in accessing a particular target site that may otherwise be difficult to reach. Typically, the introducer apparatus includes a first outer introducer sheath having a first shape and stiffness, which is used to reach a first target site. The smaller, inner introducer sheath uses the first sheath as a pathway and utilizes its increased flexibility and/or a second shape to advantageously reach a second, more distal target site that would otherwise be difficult to access using the outer introducer.
In one embodiment of an introducer apparatus used to place a pacemaker or defibrillator lead through the coronary sinus to stimulate the left side of the heart, the introducer apparatus includes an outer splittable introducer sheath and at least a second splittable introducer sheath that is coaxially inserted therein. The inner introducer sheath, which is usually introduced following initial placement of the outer introducer sheath, is designed to extend beyond the distal end of the outer introducer sheath into the coronary sinus to reach a coronary vessel for placement of a left-side lead. Preferably, the introducer sheaths comprise molecularly oriented (non-isotropic) polytetrafluoroethylene (PTFE) such as that used in the PEEL-AWAY(trademark) Introducer Sheath, although pre-scored or other types of splittable introducer sheaths may be used for certain clinical applications.
In the embodiment used to place left-side pacing or defibrillator leads, the distal tip of the first introducer sheath is designed to be placed at the ostium to, or just within the coronary sinus. To facilitate this, the first introducer sheath includes at least one preformed bend that approximates the vasculature through which the sheath is navigated, thereby reducing the likelihood of kinking the sheath during its introduction. The first introducer sheath is designed to be introduced into a larger vessel, usually over a wire guide in combination with a steerage member, such as an internal dilator, and advanced to a first target site, such as the coronary sinus. The first dilator is then removed from the outer introducer sheath and the second introducer sheath is advanced over the wire guide through the outer sheath and maneuvered to a second, more distal target site where the lead or other device is to be placed. A second dilator or obturator can be used in combination with the inner introducer sheath as it is advanced into the smaller vessel. The second introducer is partially constrained and protected by the larger first introducer sheath during its initial path to the first target site. At that point, it is advanced from the distal tip of the outer introducer sheath until it reaches the second target site. Optionally, the inner introducer sheath itself may be shaped to generally correspond to that of the outer introducer sheath and provide greater protection against kinking, or it can be designed to assume the shape of the outer introducer sheath when placed therein. Additionally, a curve may be added to the distal portion of the inner introducer sheath to facilitate access of the desired site, which often involves making a relatively acute lateral bend, such as the case with the coronary sinus ostium and ostium cardiac veins.
In another aspect of the invention, a preformed obturator may be used with either or both introducer sheaths to help steer, position or rotate the mated sheath through the vasculature. For example, in an application used to place pacing or defibrillator leads into the coronary sinus and coronary veins, an obturator can be placed into the inner sheath as it tracks over the wire guide to help provide the torque and steerability needed to make the tight turn from the coronary sinus into a coronary vein. To allow for maximum maneuverability, the obturator is given a shape that is compatible with the shape of the introducer sheath to allow for maximum maneuverability. The obturator includes a small central lumen so that both it and the introducer sheath can be fed over a wire guide already in place at the target site. After the introducer sheath and obturator are advanced to the target site, the obturator is removed. Another method of positioning the introducer apparatus includes use of a steerable or deflecting tip catheter or wire guide within the passageway of the sheath. The steerable device is usually removed from the outer introducer sheath for placement of the inner introducer sheath through which the lead or other device is navigated to the ultimate target site. As an alternative to adding one or more preformed curves to the introducer sheaths themselves and/or the steerage members used in their placement, the steerable device may be used as the sole means for providing a curved shape to outer and/or inner introducer sheaths.
Still another aspect of the invention includes adding radiopaque markings to the distal end of inner and/or outer introducer sheaths, dilators, or obturators to augment visualization under fluoroscopy. Radiopacity can achieved by incorporating radiopaque powders, such as barium sulfate or tantalum powder, into the polymer comprising the sheath material, or a separate radiopaque marker, e.g., a metal band, or an annular ring of radiopaque paint or other type of indicia can be affixed to, or printed onto the introducer sheath.
Yet still another embodiment of the invention includes adding an inflatable balloon to the distal portion of the inner or outer introducer sheath which provides a seal against backflow during injection of contrast media. During certain placement of the devices within the coronary vasculature or other vessels, it is often desirable to be able to inject contrast media to improve visualization under fluoroscopy. In some situations, especially in the cardiac veins, the backflow of blood prevents the injected media from traveling to the desired site. The balloon is made to be carried away either intact, by being attached to only one half of the splittable shaft or by comprising two separate balloons that are attached to the respective halves of the splittable sheath, or the balloon is designed to split into two or more portions by including a predetermined separation line, such as a seam, that splits the balloon open when the shaft is split.
In still yet another embodiment, either the first or second introducer sheath can include a retention means to help prevent dislodgement from the target site. This can include one or more inflatable balloons or other atraumatic elements, such a series of bidirectional projections that prevent egress of the device.